Most modern automobiles are equipped with a hydraulic power steering system. A hydraulic power steering system typically comprises a hydraulic circuit carrying a pressurized fluid (e.g., oil) from a reservoir to a steering actuator via a pump, which is mounted on an engine accessory drive. As a vehicle steering wheel is moved, the steering gear uses hydraulic pressure from the pump to assist with turning the vehicle wheels. The hydraulic power steering system generates heat during this process. When the power steering system overheats, it can cause damage to the power steering pump.
Other attempts to address hydraulic power steering system overheating problems typically include adding a power steering fluid cooler to the system. The cooler acts by exchanging heat from the fluid into the air, and thus scenarios where airflow through the engine is limited may not provide enough cooling to limit pump damage. For example, air flow is limited in scenarios wherein vehicle speeds are low. Further, in cold weather, the engine cooling fan may not activate, thus limiting air flow through the cooler.
Other attempts to address hydraulic power steering overheating include positioning a temperature sensor within the hydraulic fluid circuit. One example approach is shown by Desjardins et al. in U.S. Pat. No. 7,155,907. Therein, a thermoreactive control valve is placed at the inlet of the hydraulic fluid reservoir. The control valve is further coupled to a cooling fan, such that the control valve controls and limits operation of the cooling fan based on the temperature of the hydraulic fluid.
However, the inventors herein have recognized potential issues with such systems. As one example, the addition of a dedicated control valve or temperature sensor to the power steering system increases the manufacturing costs of the vehicle. Further, the output of such a valve or sensor may lag behind the real-time temperature of the hydraulic fluid. This may result in a delayed response from the cooling fans, which may fail to mitigate damage from an overheating power steering system.
In one example, the issues described above may be addressed by a method that includes adjusting operation of an engine cooling fan based on an engine speed and a steering wheel angle; and operating the engine cooling fan for a duration. In this way, the air flow through the steering cooler is increased in response to heat generation in the steering system, thereby decreasing pump overheating issues.
As one example, the cooling fan may be activated for a duration based on the engine speed and steering wheel angle. The duration may thus be proportionate to an inferred power steering fluid temperature, thereby eliminating the need for a dedicated power steering fluid temperature sensor. In this way, the operational elements which have the greatest impact on power steering overheating may be utilized to actively prevent system overheating.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.